The stutter you see is happening because the font file used by your menu is not downloaded at the start of your document load. If you open up Chrome's developer tools, go to the network tab, and watch requests coming through (with cache on or off) you'll see that http://getrep.me/font/proxima-nova/proximanova-bold-webfont.woff2 is being downloaded when you hover a menu. This is because on load, no text exists on the page which needs the font, so it is not yet downloaded.